Proof-of-Principle Experiment for Nanoparticle-Assisted Laser Wakefield Electron Acceleration

Abstract

We demonstrate for the first time a proof-of-principle experiment for nanoparticle-assisted laser wakefield acceleration. Nanoparticles generated through laser ablation of an aluminium target were introduced into a helium plasma and used to trigger the injection of electrons into the nonlinear plasma wake excited by an 800 nm wavelength, 1.8 J energy, femtosecond duration pulse laser. High-energy electron beams were produced, observing a significant enhancement of the electron beam energy, energy spread and divergence compared with the case when electrons are self-injected. For instance, the best quality electron bunches presented peak energy up to 338 MeV with a relative energy spread of 4.7% and a vertical divergence of 5.9 mrad. The initial results are very promising and motivate further theoretical and experimental research into developing the nanoparticle-assisted laser wakefield acceleration.

Nanoparticle-insertion scheme to decouple electron injection from laser evolution in laser wakefield acceleration

“…These metal nanoparticles usually have diameters below 100 nm 22 , 23 . Aluminum nanoparticles, generated by a 3-ns 532-nm ablation laser, have been proposed to trigger electron injection in our previous study 24 . This study demonstrated experimentally that a single nanoparticle is able to trigger electron injection and produce low-divergence electron bunches with a charge of a few pC.…”

Multi-GeV Laser Wakefield Electron Acceleration with PW Lasers

“…At this condition, self-injection is not possible. Recently, electron injection mechanisms, such as ionization injection [39][40][41], density shock injection [42,43], and nanoparticle insertion [44,45], have been proposed and demonstrated. Because the laser should propagate 10 m for 100 GeV acceleration, the electron injection process should not degrade laser properties and should occur only at the beginning of the medium.…”

“…A numerical study showed that a nanoparticle in plasma could facilitate a controllable injection to produce a high-quality 5-GeV electron beam with a 0.5-PW laser pulse [44]. Furthermore, a recent experimental study demonstrated nanoparticle-assisted laser wakefield acceleration with a nanoparticle-mixed helium gas jet [45]. Although controlling precisely the location of nanoparticles in plasma is challenging, the nanoparticle injection method can be a promising method to realize a 100-GeV electron beam with 10-PW-class lasers.…”

Stable and high quality electron beams from staged laser and plasma wakefield accelerators

“…At densities around 10 18 cm −3 the acceleration gradient in these accelerators is thus several orders of magnitude higher than the breakdown fields in conventional radio-frequency (RF) accelerators (∼ 100 MV m −1 ), al-lowing for a significant downsizing of the accelerator. LWFA experiments are routinely performed at numerous high-power laser facilities [3][4][5][6][7][8][9][10][11] and reach high charge (∼ nC) [12,13] combined with an ultra-short bunch duration (∼ 10 fs) [14,15], resulting in high peak currents of tens of kA [13,16]. Furthermore, the bunches typically have a few-micrometer source size at the exit of the accelerator [17][18][19], which is paired with few-mrad divergence [12,20].…”